Similar to act_gact/act_mirred, act_bpf can be lockless in packet processing.
Also similar to gact/mirred there is a race between prog->filter and
prog->tcf_action. Meaning that the program being replaced may use
previous default action if it happened to return TC_ACT_UNSPEC.
act_mirred race betwen tcf_action and tcfm_dev is similar.
In all cases the race is harmless.
Long term we may want to improve the situation by replacing the whole
struct tc_action as single pointer instead of updating inner fields one by one.
Signed-off-by: Alexei Starovoitov <a...@plumgrid.com>
---
net/sched/act_bpf.c | 15 +++++----------
1 file changed, 5 insertions(+), 10 deletions(-)
diff --git a/net/sched/act_bpf.c b/net/sched/act_bpf.c
index 1b97dabc621a..2b8c47200152 100644
--- a/net/sched/act_bpf.c
+++ b/net/sched/act_bpf.c
@@ -43,10 +43,8 @@ static int tcf_bpf(struct sk_buff *skb, const struct
tc_action *act,
if (unlikely(!skb_mac_header_was_set(skb)))
return TC_ACT_UNSPEC;
- spin_lock(&prog->tcf_lock);
-
- prog->tcf_tm.lastuse = jiffies;
- bstats_update(&prog->tcf_bstats, skb);
+ tcf_lastuse_update(&prog->tcf_tm);
+ bstats_cpu_update(this_cpu_ptr(prog->common.cpu_bstats), skb);
/* Needed here for accessing maps. */
rcu_read_lock();
@@ -77,7 +75,7 @@ static int tcf_bpf(struct sk_buff *skb, const struct
tc_action *act,
break;
case TC_ACT_SHOT:
action = filter_res;
- prog->tcf_qstats.drops++;
+ qstats_drop_inc(this_cpu_ptr(prog->common.cpu_qstats));
break;
case TC_ACT_UNSPEC:
action = prog->tcf_action;
@@ -87,7 +85,6 @@ static int tcf_bpf(struct sk_buff *skb, const struct
tc_action *act,
break;
}
- spin_unlock(&prog->tcf_lock);
return action;
}
@@ -294,7 +291,7 @@ static int tcf_bpf_init(struct net *net, struct nlattr *nla,
if (!tcf_hash_check(parm->index, act, bind)) {
ret = tcf_hash_create(parm->index, est, act,
- sizeof(*prog), bind, false);
+ sizeof(*prog), bind, true);
if (ret < 0)
return ret;
@@ -325,7 +322,7 @@ static int tcf_bpf_init(struct net *net, struct nlattr *nla,
goto out;
prog = to_bpf(act);
- spin_lock_bh(&prog->tcf_lock);
+ ASSERT_RTNL();
if (ret != ACT_P_CREATED)
tcf_bpf_prog_fill_cfg(prog, &old);
@@ -341,8 +338,6 @@ static int tcf_bpf_init(struct net *net, struct nlattr *nla,
prog->tcf_action = parm->action;
prog->filter = cfg.filter;
- spin_unlock_bh(&prog->tcf_lock);
-
if (res == ACT_P_CREATED)
tcf_hash_insert(act);
else
--
1.7.9.5
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